Effect of Allergen Exposure Reduction Efforts on Asthma Outcomes

More research with adequate study populations is necessary to determine whether indoor allergen reduction interventions can improve asthma outcomes.

There is insufficient evidence that specific allergen reduction interventions are associated with improvement in asthma control measures or pulmonary physiology. However, exacerbations may be diminished with the use of high-efficiency particulate air-filtration (HEPA) vacuum cleaners and pest control, according to a study published by the Journal of Allergy and Clinical Immunology.

Researchers performed a systematic review of the literature to evaluate the effectiveness of allergy reduction interventions on asthma outcomes. Acaricide, air purification, carpet removal, the use of HEPA vacuum cleaners, the use of mattress covers, mold removal, pest control, and pet removal were all interventions assessed in the 59 randomized and 8 nonrandomized studies selected. Some studies assessed only one component (n=37), while others assessed multiple components (n=30). Researchers assessed the risk for bias in randomized controlled trials with the Cochrane Risk of Bias instrument and with the Newcastle-Ottawa scale in nonrandomized studies.

Although acaricide may have reduced dust mite allergens, no improvements in pulmonary physiology or asthma symptoms were observed. In addition, no improvement in asthma control or exacerbations was seen as a result of air purification; however, some studies reported an improvement in asthma symptoms, reduced allergen levels, and decreased absenteeism. The use of air purification improved quality of life according to one study, but other studies found no effect. Carpet removal reduced allergen levels in some studies but was inconclusive in others.

The use of a HEPA vacuum cleaner reduced asthma exacerbations but did not change asthma medication use or affect work/school absenteeism. There was also insufficient evidence to determine the effect of using HEPA vacuum cleaners on asthma control and pulmonary physiology measures. Although an improvement in asthma symptoms was seen in children, it was not observed in a mixed population of children (children, adolescents, and adults). Quality of life improvement was seen only in children younger than 12 years of age.

Despite a reduction in dust mites observed with the use of impermeable mattress covers, there were no differences seen in asthma control, exacerbations, use of inhaled corticosteroids, rescue medication use, pulmonary physiology, quality of life, or self-reported asthma. In multicomponent intervention studies, emergency department use, hospitalizations, and acute care visits were not improved with this intervention. Pulmonary physiology and quality of life were also not affected by impermeable mattress covers.

Asthma symptom improvement was the only outcome improved with mold removal. Self-reported asthma symptoms improved with pest control; unfortunately, results were inconclusive for asthma control, medication use, and pulmonary physiology measures. Emergency department visits and hospitalizations were not changed by pest control; however, exacerbations were reduced, school absenteeism was decreased, and quality of life in children was improved. Allergen levels and asthma symptoms improved with the reduction of cockroaches.

The evidence was inconclusive regarding the effect of pet removal on hospitalizations, medication use, and follow-up visits.

Researchers concluded that there was a lack of high-strength or consistent evidence in the literature regarding allergen reduction interventions that would suggest an improvement in primary outcomes. However, low-to-moderate strength evidence for some interventions was found in the literature review. Therefore, clinicians should consider a patient's individual sensitives to certain allergens and focus on recommending interventions that address the reduction of exposure to triggers.